Co-articulation problems are often evident in user utterances including numeric sequences having one or more digit strings. The co-articulation problem may occur in any spoken language, particularly in tonal-based languages such as, e.g., Mandarin, Min, Taiwanese, and Cantonese. For instance, a numeric sequence having a digit string of “5, 5, 5” in English phonetically equates to “wu, wu, wu” in Mandarin. In some instances, the “wu, wu, wu” utterance may come across, e.g., to a speech recognition system, as “wu, wu”, “wu, er, wu”, “er, er, er”, or some other similar inaccurate variation of the actual utterance.